You can't use CONVERT_EXPR to convert between two class types, and it was breaking copy elision.
Unfortunately, this patch breaks symmetric-transfer-00-basic.C, where susp_type is Loopy<int>::handle_type. How is this supposed to work? gcc/cp/ChangeLog: * coroutines.cc (expand_one_await_expression): Change conversion to assert. --- gcc/cp/coroutines.cc | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/gcc/cp/coroutines.cc b/gcc/cp/coroutines.cc index eca01abcb7a..568f2edf67d 100644 --- a/gcc/cp/coroutines.cc +++ b/gcc/cp/coroutines.cc @@ -1728,7 +1728,9 @@ expand_one_await_expression (tree *stmt, tree *await_expr, void *d) } else { - r = build1_loc (loc, CONVERT_EXPR, void_coro_handle_type, suspend); + gcc_checking_assert (same_type_ignoring_top_level_qualifiers_p + (void_coro_handle_type, susp_type)); + r = suspend; r = build2_loc (loc, INIT_EXPR, void_coro_handle_type, data->conthand, r); r = build1 (CONVERT_EXPR, void_type_node, r); append_to_statement_list (r, &body_list); base-commit: 43faf3e5445b571731e52faa1be085ecd0a09323 -- 2.31.1